I personally think that neither should determine that. Both questions are unable to determine whether the religion is true; so why would it be used to determine whether or not people have the right to follow it. However, putting that aside, I think the best answer would be how good their followers are. It doesn't determine whether the religion is true or not but it rids us of the toxic religions that spread negative messages. Considering how much racism, homophobia, transphobia, and sexism is in most religions it'd be interesting to see most religions cease.
Including commonly followed religions like Catholicism.
